The present invention relates to an ink jet recording head in which a part of each pressure generating chamber communicating with nozzle orifices for ejecting ink droplets is formed with a vibration plate, a piezoelectric element is provided on the vibration plate interposed, and an ink droplet is ejected by a displacement of the piezoelectric element and a method of manufacturing the recording head, and an ink jet recording apparatus.
The ink jet recording head in which a part of each pressure generating chamber communicating with nozzle orifices for ejecting ink droplets is formed with a vibration plate, and the vibration plate by the piezoelectric element is deformed to pressurize ink in the pressure generating chamber to eject an ink droplet through the nozzle orifice, is known. This type of recording head is categorized into two types of recording heads; one uses the piezoelectric actuators of the longitudinal vibration mode in which the piezoelectric element axially expands and shrinks, and the other uses the piezoelectric actuators of the flexural vibration mode. Those types of recording heads have been put into practice.
The former recording head is advantageous in that the recording head suitable for the high density printing may be manufactured since the volume of the pressure generating chamber is varied by bringing the end face of the piezoelectric element into contact with the vibration plate. However, it has a difficult step of cutting the piezoelectric elements in a comb shape in alignment with the pitches of the nozzle orifice array, and needs another step of positioning and fixing the cut piezoelectric elements to the pressure generating chambers. In this respect, the manufacturing process is complex.
The latter recording head is advantageous in that the piezoelectric elements may be formed on the vibration plates in a relatively simple manner that a green sheet of piezoelectric material is bonded onto the vibration plates in conformity with a shape of the pressure generating chambers, and then baked. However, this recording head is disadvantageous in that since the flexural vibration is utilized, an area of some extent must be secured for each the piezoelectric element. Accordingly, it is difficult to array the piezoelectric elements at high density.
To solve the disadvantage of the latter recording head, there is proposed a technique in which a piezoelectric layer is uniformly formed over the entire surface of the vibration plate, and the piezoelectric layer is cut by a lithography process to form individual piezoelectric elements for each pressure generating chamber in accordance with arrangements of the pressure generating chambers (see JP-A-5-286131).
This technique enables to eliminate the work of bonding the piezoelectric elements to the vibration plates. Accordingly, the piezoelectric elements may be manufactured by a precise and simple process, using the lithography process. Additionally, the piezoelectric element is thinned and hence driven at high speed.
In such an ink jet recording head, the pressure generating chambers are formed penetrating the passage forming substrate in a manner that the passage forming substrate is selectively etched by anisotropic etching process from a surface of the passage forming substrate opposite to the piezoelectric-elements to the vibration plate.
When the anisotropic etching process is carried out in the form of a wet etching process using an alkaline aqueous solution, the alkaline aqueous solution or etching reaction products penetrate through the vibration plate to damage the piezoelectric elements, at the end of the etching process.
In the dry etching process, the etching is terminated indefinitely, therefore it is difficult to control the width of the vibration plate side of the pressure generating chamber. Accordingly, the pressure generating chambers cannot be formed with high accuracy by the dry etching process.
Further, in such an ink jet recording head, the pressure generating chambers are formed by the etching after the piezoelectric elements are formed. Accordingly, a position of the vibration plate side of the pressure generating chamber is instable by the dispersion in verticality of the pressure generating chambers. An accuracy of a relative position shift of the piezoelectric element to the pressure generating chambers is low, so that the ink ejecting characteristic and stability are low.